This invention relates to the art of composing lines of text from alphabetical, numerical and other similar characters, and deals more particularly with a method and apparatus for automatically, in a computer-implemented composing system, establishing through the processing of digital data an intercharacter spacing which varies from one pair of characters to another and which is dependent on the shapes of the characters, to produce a line of text of pleasing appearance.
The method and apparatus of this invention have been developed for use initially with an automated sign generator such as shown and described in copending U.S. patent application Ser. No. 401,722, filed July 26, 1982, now U.S. Pat. No. 4,467,525, and they are hereinafter described as applied to such device. However, the invention is not limited to such application and may instead find utility in many other computer-implemented systems involving the composition or generation of lines of text - particularly systems where the characters are generated from computer memory resident fonts of characters.
A problem in composing lines of text is that for a pleasing appearance various different spacings have to be used between different pairs of characters. The "proper" spacing between any two characters is a matter of judgment and in the past has often been controlled manually by the operator. For example, the automated sign maker defined by the above-identified copending patent application provides a standard spacing between each pair of characters, and the keyboard includes at least one "kern" key by means of which the operator can subtract incremental amounts from such standard spacing. In one actual embodiment of such sign maker two kern keys have been provided, one being a "1/4" kern and the other being a "1/8" kern. By pressing the "1/4" kern key, a given amount of spacing dependent on the selected character height is subtracted from the standard spacing between two given characters and by pressing the "1/8" kern key, another amount of spacing equal to one-half said given amount is subtracted from the standard spacing. Such manual editing of the intercharacter spacing is, however, time consuming and demanding of the operator and it is therefore the object of this invention to provide a method and apparatus for achieving aesthetically pleasing intercharacter spacing without need for operator intervention.
One obvious way to provide for automatic intercharacter spacing would be to provide a memory resident look-up table defining the intercharacter spacing to be used for each possible pair of characters of a font. However, since a font of characters normally includes at least a complete alphabet of upper-case letters, a complete alphabet of lower-case letters and a complete set of numerals and punctuation marks, such look-up table would be very large and unwieldly to use. A further object of the invention is therefore to provide for automated intercharacter spacing which avoids the use of a character pair look-up table but which nevertheless achieves, through digital processing, intercharacter spacings dependent on the shapes of the individual characters making up each character pair.
Other objects and advantages of the invention will be apparent from the following description and from the accompanying drawings.